Conventionally, for a working machine and a motorcycle in which an engine is mounted, safety measures for stopping the engine have been taken. This is because, when a working machine or the like having an engine falls by accident during operation, there is a fear that the working machine goes out of control of an operator. This is also because there is another fear that leaking fuel catches fire from a spark or the like resulting from a short circuit in an electrical system, which leads to an explosion.
Means for detecting a fall state of a machine is necessary to stop an engine automatically in the event of a fall. As an example of such fall detection means, a fall detection sensor configured such that a signal output from an acceleration sensor that detects a gravitational acceleration is processed by a low-pass filter or an integrator, the processed signal is then input to a comparator, and it is determined whether the machine has fallen or not is known.    Patent Document 1: WO 2009/095986